1. Field of Invention
The present invention relates generally to a composition and a method of using the composition for removal and prevention of broad spectrum microbial contamination in meat products. More specifically, the present invention relates to a method of using quaternary ammonium compounds (QAC) for inhibiting attachment of and removing a broad spectrum of microbial contamination from poultry and meat products. More specifically, the present invention relates to a method of using QAC for inhibiting attachment of and removing pathogenic toxin-producing Escherichia contamination, such as Escherichia coli O157:H7, from meat and poultry products. More particularly, the present invention relates to an improved treatment method of spraying QAC on the poultry and meat products to prevent broad spectrum microbial contamination. The present invention also relates to new formulations of QAC including solubility and viscosity enhancing agents.
2. Description of the Prior Art
Prevention of foodborne illness by microbiological contamination is of major concern to the poultry and meat processing industry, regulatory agencies, and consumers. A recent report from the Food Safety & Inspection Service (FSIS) of the United States Department of Agriculture (Federal Register, Feb. 3, 1995) estimates that over 2 million cases of foodborne illnesses are produced annually by microbial contamination in the United States, with an associated cost of over $1 billion. In their efforts to provide a product completely free of microbial contamination, poultry and meat processors have encountered major difficulties in removing these microorganisms that adhere or attach vigorously to poultry and meat tissues intended as food products. If contaminating microorganisms do not attach to the surface of the food, they can be easily rinsed off. However, the microorganisms that become strongly attached cannot be removed by rinsing and are quite resistant to removal by chemical or physical means.
Salmonella typhimurium contamination has been of special concern to the poultry processing industry because the organism is often present on live birds. Poultry processors have had great difficulty in removing microorganisms such as S. typhimurium, that attach or adhere to poultry tissues. A variety of chemical and physical approaches have been suggested for use during poultry processing to eliminate S. typhimurium contamination of carcasses and minimize cross-contamination among carcasses. Trisodium phosphate (TSP) has been utilized in poultry processing for suppressing S. typhimurium; however, studies report conflicting results on the efficacy of TSP against Salmonella.
U.S. Pat. No. 5,366,983 discloses a method for removing or preventing Salmonella contamination of meat products by treating with an effective amount of an aqueous solution of a QAC. Specifically, quaternary ammonium cationic surfactants, such as alkylpyridinium, particularly cetylpyridinium chloride (CPC) and cetylpyridinium bromide (CPB) were effective in removing S. typhimurium from poultry. This patent, however, does not disclose that QAC are effective in treating meat products against any other genus of microorganisms than Salmonella.
However, foodborne illnesses caused by other pathogenic and spoilage bacteria than Salmonella have increasingly become a problem for poultry and meat processors. A list of these bacteria with the products in which they have been identified is presented in Table 1:
TABLE 1 ______________________________________ INCIDENCE OF PATHOGENIC AND SPOILAGE BACTERIA Patho- Spoil- Microorganism Poultry Beef Pork gen age ______________________________________ Aeromonas hydrophila X X X X Arcobacter butzleri X X X Bacillus cereus X X X X Campylobacter jejuni X X X X Escherichia coli O157:H7 X X X X Listeria monocytogenes X X X X Salmonella typhimurium X X X X Staphylococcus aureus X X X X ______________________________________
Among these contaminating microorganisms listed in the table, Escherichia coli O157:H7 is a special concern to the meat and poultry industry because of its virulence, severity of the illness produced, and associated mortality. E. coli O157:H7 produces strong "shiga-like" toxins that lead to blood clotting abnormalities, kidney failure (hemolytic uremic syndrome), and death. Even if recovery from the acute illness is complete, 15-30% of infected people with hemolytic uremic syndrome will have evidence of chronic kidney disease. The risks associated with contamination with E. coli O157:H7 are compounded by its reported resistance to antibiotics. In 1993, between 8,000-16,000 cases of foodborne illness were produced by E. coli O157:H7 with an estimated cost of between 0.2 and 0.5 billion dollars.
Listeria monocytogenes has been found in meat, vegetables, and various milk products; and may cause sepsis, meningitis, and disseminated abscesses. L. monocytogenes is a cold tolerant microorganism capable of growing under refrigeration. In 1993, about 1,700 cases of foodborne illness were produced by L. monocytogenes with an estimated cost of between 0.1 and 0.2 billion dollars.
Another microorganism of concern in the food industry is Aeromonas hydrophila which causes spoilage in the food and meat processing industry and which reduces the shelf life of these products.
Presently, there is no known bactericidal compound which is effective at preventing and removing contamination in poultry and meat products against a broad spectrum of gram positive, gram negative, aerobic, facultative anaerobic, and microaerophilic microorganisms. The present inventors have discovered that QAC are effective against a broad spectrum of different microorganisms which produce foodborne illnesses. This sensitivity of a broad spectrum of pathogenic microorganisms could not have been predicted by the disclosure in U.S. Pat. No. 5,366,983 disclosing the sensitivity of only Salmonella to QAC.
Sensitivity of a microorganism against a particular antimicrobial agent is not predictive of the sensitivity of other microorganisms to the same agent. It has been believed that antiseptics or germicides have a continuous spectrum of activity but the relative susceptibilities of different microorganisms must be considered. For example, the germicide, hexachlorophene is primarily effective against Gram positive microorganisms, and cationic antiseptics are not effective against sporulating organisms. Some Gram negative microorganisms, such as Pseudomonas cepacia, have been known to grow in solutions of the drug, benzalkonium chloride. Other bacteria have been known to be capable of growing in 70% ethanol (Harvey, S. C., Antimicrobial Drugs in Remington's Pharmaceutical Sciences, 18th Ed., Mack Publishing Co., pp. 1163-1241 1990).
In regard to the treatment of meat products, it has been reported that Listeria is more resistant to the action of TSP than Salmonella or E. coli (Somers, E. B. et al., Int. J. Food Microbiol., 22:269-276, 1994). Further, (Breen et al., J. Food Sciences, 60:1991-1996, 1995) demonstrated that TSP is much less effective in inhibiting Salmonella growth than it is in detaching this organism.
Most importantly, however, is the discovery that QAC are effective against E. coli O157:H7 in suspension in liquids, and attached to meat products as well as inhibiting the attachment of this bacteria to meat products. It has been reported that E. coli O157:H7 shows resistance towards broad spectrum antimicrobial agents, such as tetracycline, streptomycin, sulfisoxazole (Kim et al., J. Infect. Dis., 170:1606-1609, 1994) and oxytetracycline (Ciosek et al., Med. Weter. 40:335,338:1984), whereas these same agents are very active against regular non-toxin-producing strains of E. coli.
It cannot be predicted that different antimicrobial agents or biocides will penetrate a given microorganism in the same manner as it will another microorganism. The degree of glycocalyx formation by a given species of attached bacteria, the presence of a lipopolysaccharide- and phospholipid-containing cell envelope in gram negative bacteria, the presence of lipoprotein as in most enteric bacteria and Pseudomonas, and the presence of porin protein channels, for example in E. coli and Salmonella, are examples of bacterial characteristics which may play a role in the effectiveness of an antimicrobial agent against a particular microorganism (Fulton et al., Structure in Medical Microbiology, 3rd Ed., pp. 37-54, 1991).
In summary, there is evidence that the activity of a given antimicrobial agent against a particular microorganism cannot be inferred by its activity against other microorganisms, but rather can only be determined under conditions of use. This is especially true for microorganisms which are attached to surfaces as in the case of contamination of food. The present inventors have shown that bacteria suspended in liquids are generally more susceptible to antimicrobial agents than the same bacteria attached to surfaces. As a result of increasing numbers of illnesses caused by foodborne pathogenic microorganisms, the poultry and meat processing industries now require more effective processes for the removal and prevention of a broader spectrum of microorganisms, and particularly for toxin-producing Escherichia, such as E. coli O157:H7, which are known to cause serious human diseases as a result of food contamination.